Method of cleaning masonry



United States Patent Office 3,505,l l2 Patented Apr. 7, 1970 3,505,112 METHOD OF CLEANING MASONRY Roddy E. Kettler, Waco, Tex. No Drawing. Filed Sept. 5, 1967, Ser. No. 665,246 Int. Cl. C03c 23/00 US. Cl. 134-2 8 Claims ABSTRACT OF THE DISCLOSURE A method of cleaning masonry comprising a non-pressure application of a water solution of about 6% sodium hypochlorite with traces of Prussian blue, sodium oxide, and potassum sulphate; resting the treated surface for from four to six minutes, thereafter applying a soft water spray at 300 p.s.i., followed, optionally, by non-pressure spray with water solution of monopotassium persulphate.

It is an object of this invention to provide a purely chemical method of cleaning the surfaces of buildings such as stone, brick and concrete surfaces of all nature, and including asbestos siding or slate when used as roofing or siding. Heretofore, for such purposes, resort has been had to sand blasting or to treatment with hydrochloric acid. Both the sand blasting and the acid treatments not only are detrimental to the surface being cleaned but dangerous to the personnel engaged in the cleaning and in the case of sand blasting in particular, a large scale operation has a considerable nuisance potential for a considerable distance around the job being sand blasted.

The present invention is operative with practically a neutral solution which in no way is dangerous or deleterious to the job being done or to the personnel handling it, and produces excellent results in less time than would be occupied through the use of other methods.

By this improved method, the overall job time is perceptibly shortened and the overall cost is lowered.

The method is essentially a two-step process with a third step optional in extremely stubborn cases.

To carry out the first stage of the process, a water solution is made having the following active ingredients by weight:

The solution just described is sprayed on the surface to be cleaned but under distinctly low pressure. All that is required is thorough wetting and penetration of the usually rough and porous surface. The time that the solution is allowed to remain on the surface is not particularly critical on the maximum side. Naturally, enough time has" to be allowed for the primarily bleaching action of the solution to take place and economically, of course, it is desirable to complete the job as rapidly as possible. Therefore, in practice, the original application of the first solution is allowed to remain in place from four to six minutes, though no ill effect would result if the time were greatly increased.

The second stage involves a high pressure wash with soft water. This soft water spray is accomplished at short range under a pressure of about 300 p.s.i. which serves not only to remove the previously applied active solution but to free up and wash away by mechanical action such dirt as soot particles which are not particularly affected by the active ingredients of the first solution, though these ingredients do appear to have a loosening effect making mechanical removal of such particles as soot easy of accomplishment by the second high pressure spray.

As a water softener for the second stage, a mixture of sodium phosphate and soda ash is prepared. The essential characteristic of the second water wash is that the water be soft and any softening process will do for this purpose. The amount of softening compound used will, of course, depend on the initial kind and degree of hardness of the water. In stubborn cases, even following the first two washes, there may be a few dark spots left on the masonry. If this happens, a third wash is used.

Preferably, this is a water wash containing 5% by weight of monopotassium persulphate. This is applied at low or no pressure similar to the manner of application of the first spray and is permitted to dry in place. As an alternative to monopotassium persulphate is the use of a water wash containing from 2 /2 to 3% by weight sodium hypochlorite. It has been found that when monopotassium persulphate or sodium hypochlorite be used, the solution remains active even after it is dried on the masonry surface and the result is a rather rapid fading of such residual spots as may be left after the first two washes.

It is to be noted that none of the washes involves chemicals of such nature or in such concentration as to offer the slightest deleterious effect upon either the masonry or on the personnel utilizing the process. The second wash is at high pressure, and this wash should be applied with the nozzle close to the work. It is highly effective in mechanical removal of dirt which presumably was previously loosened by the first wash.

What is claimed is: 1. A method of chemically cleaning a masonry surface having been exposed to an outdoor environment comprising the steps of:

applying a dilute aqueous solution consisting of about 6% by weight sodium hypochlorite with trace amounts of whitening agents taken from the group consisting of sodium oxide, Prussian blue, potassium sulphate, and mixtures thereof onto said surface,

saturating the pores of said surface with said solution for at least 4 minutes to effectively attack adhered foreign substances contained therein and thereby loosening said substances from said surface and pores,

washing away the loosened substances by impingement of a high pressure spray of softened water.

2. A method in accordance with claim 1, wherein the hypochlorite solution is sprayed at low pressure.

3. A method in accordance with claim 2, wherein the saturating time ranges from about 4 minutes to about 6 minutes.

4. A method in accordance with claim 2, wherein the softened water is sprayed at about 300 p.s.i. pressure with the spray nozzle being placed in close proximity to said surface for more effective washing.

5. A method in accordance with claim 1, followed by the steps of:

spraying a dilute aqueous solution consisting of sodium hypochlorite onto said treated surface,

drying said surface and thereby providing a residue of sodium hypochlorite on said surface to subsequently further react thereon.

6. A method in accordance with claim 5, wherein the second application of treating solution consists of about 3% by weight sodium hypochlorite.

7. A method in accordance with claim 1, followed by the steps of:

spraying a dilute aqueous solution consisting of monopotassium persulphate onto said treated surface, drying said surface and thereby 3,505,112 3 4 providing a residue of monopotassiurn persulphate 0n FOREIGN PATENTS said surface to subsequently further react thereon. 8. A method in accordance with claim 7, wherein the 2/1959 Canada second application of treating solution consists of about 5/1939 Great Bntam' 5% by weight monopotassium persulphate,

References Cited UNITED STATES PATENTS 5 MORRIS O. WOLK, Primary Examiner B. S. RICHMAN, Assistant Examiner 147,250 2/1874 Elliott 134-2 XR 1,355,074 10/1920 Cleveland 13436XR 10 1,370,188 3/1921 Cleveland 13436 XR 3 42 1,667,683 4/ 1928 Thompson et a1. 2,768,101 10/1956 Fairchild 134-38 XR 

